An example of a stairlift is described in U.S. Pat. No. 5,533,594. Known stairlifts comprise a rail, which is mounted above the stairway on the inner or outer wall of the stairwell, a platform (for instance a chair, or a floor for, for instance, a wheelchair) and a drive mechanism for moving the platform along the rail and thereby along the stairway. It is further known to provide a second drive mechanism to keep the platform horizontal. This second drive mechanism rotates the platform about a horizontal shaft relative to the rail, depending on the gradient of the rail at that location.
Above-mentioned U.S. Pat. No. 5,533,594 describes how, during getting on and getting off, use is also made of the rotation of the platform about a vertical shaft, which is known in this field by the term “swiveling”. In this manner, the transported person is turned to the step at the top and bottom of the stairway. For this, two positions are needed (for the top and the bottom of the stairway, respectively) which are mutually rotated relative to the rail through 180 degrees. En route, the platform is fixed in a transport position, which is, for instance, midway between the two positions for getting off, with the transported person facing the wall.
The patent specification describes how, for swiveling, use can be made of a combined rotation and translation movement to prevent the platform on the stairlift from hitting the wall during the swiveling from the positions for getting on and getting off to the transport position.
The space available in a stairwell is a factor which determines whether a stairlift can be placed. It will be clear that placement is not possible if the platform does not fit between the walls of the stairlift or if there is too little headroom left under the ceiling of the stairwell. In particular, this is often the case in stairways with bends. Also, swiveling for getting on and off is not possible if the stairwell does not provide sufficient space for this.